The collective goal of the proposed research is to analyze the essential elements in signal transduction and processing common to diverse chemosensory receptors, and to elucidate unique adaptations in these pathways which enable them to subserve specific receptor functions under a variety of environmental conditions. In this multi-disciplinary endeavor, a collaborative research will facilitate the exchange of ideas and data and support the mutual progress of the constituent projects. Common themes amongst the four projects include: 1) environmentally-mediated plasticity in sensory function, 2) parallel processing of sensory input, and 3) multi- modal detection capabilities. The first project examines odorant signal processing in zebrafish, where general odorants vs. pheromones activated signal-specific transduction cascades which are proposed separately in lateral and medial olfactory bulbs, respectively. Experiments will examine the hypothesis that processing of these distinct sensory signals occurs independently via different mechanisms in these two regions of the bulb. The second project investigates chronic hypoxia-induced adaptations in rat petrosal ganglion chemoafferent neurons which innervate arterial chemoreceptors of the carotid body. This project will characterize altered phenotypic expression in these neurons, the mechanisms which control neuroplastic changes, and the relationship between chemoafferent neuron adaptation and altered chemotransmission in the carotid body. The third project hypothesizes that cross-talk during odor transduction plays a vital role in the coding of odor mixtures in single squid olfactory receptor neurons. Various steps in odorant transduction cascades will be examined to determine the mechanisms underlying odor mixture interactions. These studies will further elucidate how the mixture code for odor recognition is generated across the sensory epithelium. Finally, the fourth project will test the hypothesis that, in addition to chemical transmission, electrical coupling via gap functions exists between O2-sensitive type I cells in rat carotid body and their chemoafferent nerve terminals. These findings may help resolve long standing questions regarding the physiological role of neuroactive agents released from type I cells in response to hypoxia.